The present invention relates to a post-processing apparatus which makes booklets by trimming an edge of sheets, and an image-forming apparatus equipped with the post-processing apparatus.
There has been used in the printing industry, a post-processing apparatus equipped with a trimming apparatus for aligning an edge by trimming the edge of sheets of paper after some processes such as a center-folding process and a saddle-stitching process of the sheets.
Lately, there has been provided a post-processing apparatus equipped with a trimming apparatus for aligning an edge by trimming the edge of sheets of paper, to which processes such as a center-folding process and a saddle-stitching process of the sheets have been carried out after receiving sheets on which images were formed by image-forming apparatuses such as a copying machine and a printer.
Apparatuses described below are known as a trimming apparatus mentioned above.
FIG. 11 shows a cross-sectional view of the main parts of trimming apparatus 900 which trims an edge of sheets S to which a center-folding and a saddle-stitching have been carried out.
The numeral 901 represents an upper blade which moves vertically and trims uneven edges of sheets S in cooperation with a lower blade 902 which is fixed to the body.
The numeral 903 represents an edge holding member which holds a portion of the sheets S near the edge, and is urged by spring 904 in conjunction with a lowering motion of the upper blade 901 so as to hold the portion of the sheets S to prevent the sheets S from sliding.
The numeral 905 represents a fold-holding means to eliminate a swell of the sheets around the fold.
The numeral 906 represents a stopper to stop sheets S fed to the trimming position by inserting means 907 and 908 at the prescribed position.
By means of the above-mentioned structure, the sheets S are inserted into the trimming position by inserting means 907 and 908, and fold-holding means 905 lowers to eliminate a swell of the sheets around the fold when the sheets contact the stopper 906 and stop there.
Subsequently, upper blade 901 trims uneven edges of the sheets S in cooperation with lower blade 902, after the upper blade 901 lowers and a portion of sheets near the edge is held by edge holding member 903.
Post-processing apparatuses equipped with trimming apparatuses of this kind have been disclosed (for example, refer to Patent Document 1).
[Patent Document 1] TOKKAI 2000-198613
The number of sheets on which an edge trimming is carried out is extensive from a small number (for example, about five before being folded) to a large number (for example, about fifty before being folded) and a large force is necessary for pressing edge holding member 903 to prevent the sheets from sliding during the trimming because a large force is necessary to cut sheets when a large number of sheets are trimmed.
However, according to the structure described in Patent Document 1, there are cases, in which the trimmed face is not even, caused by sliding of sheets when a large number of sheets are treated, because a portion of sheets near the edge is held by force of spring 904.
For preventing this problem, there is an idea to move edge holding member 903 by a driving means independent from one for upper blade 901.
In this case, although increase of power of the driving motor used for driving means can be considered to increase pressing force of edge holding member 903, it is not expedient because of an increase of electricity consumption, upsizing of the body and a raise in cost increase.
Accordingly, it is preferable to use a motor as small as possible and to obtain demanded pressing force for edge holding member 903, through gear reduction.
When the ratio of the gear reduction is large, the traveling speed of the edge holding member 903 is lowered and it causes a problem that it takes long to hold the sheets S, and therefore, the traveling time of edge holding member 903 may become longer than the process time of the upstream side of the post-processing apparatus or the process time of the image-forming apparatus, leading to the decline of productivity when the number of the sheets is small.